Photoelectric cathode



Sgph 29, 1942. P. GORLICH 2,297,467

v PHOTOELEQTRIC CATHODE I Filed April 22, 1940 INVENTOR.

BY Paul G'rlz'cfi ATTORNEYS Patented Sept. 29, 1 942 OFFICE PHOTOELECTRIC CATHODE Paul Giirlich, Dresden, Germany; vested in the Alien Property Custodian Application April 22, 1940, Serial No. 330,964 In Germany April 26, 1939 3 Claims.

The invention relates to improvements in photo electric cathodes and secondary electron emitting electrodes and particularly is directed to a further improvement of the photo electric cathode disclosed in my United States Patent No. 2,172,164 issued on the th day of September 1939.

The photo electric layer of my prior invention, which layer may also be used as a secondary electron emitting electrode, comprises an oxidised metal base, a layer of an alkali metal thereon, and a thin layer of a metal forming the top coating of said alkali metal layer, said top coating having a lower electric conductivity than said alkali metal. Such a photo electric cathode possess a very high sensitiveness, particularly in the short-wave or ultraviolet zone of the spectrum.

The object of the present invention is to increase 'the light sensitiveness of the cathode still more toward the short-wave zone of the spectrum.

Another object of the invention is to increase the thickness of the light sensitive layer without decreasing the relative sensitiveness of the same.

In the drawing:

Fig. 1 illustrates diagramatically the manner of producing a photo electric cathode of the present invention.

Fig. 2 illustrates diagrammatically the mutual penetration of the various layers of the photo electric cathode,

Fig. 3 illustrates diagrammatically the manner of producing a photo electric cathode of greater thickness.

Fig. 4 illustrates diagrammatically a photo electric cathode of still greater thickness.

According to the present invention the sensitiveness of the photo electric cathode is increased toward the short-Wave zone of the spectrum by applying or precipitating the alkali metal directly upon the surface of the base formed by a good electric conductor, such as silver or copper. In other words, the electrically conductive base is not oxidised as is disclosed in my prior invention. Therefore, Fig. 1 illustrates an alkali metal layer of caesium (Cs) directly on top of the electrically conductive base of silver (Ag). After this is done, the caesium layer is covered in the same manner as described in my prior Patent No. 2,172,164 with a thin layer of a metal having a lower electric conductivity than the alkali metal. Such a metal may be bismuth (Bi) antimony (Sb), or lead (Pb). In the present instance the Fig. 1, illustrates a bismuth layer.

Fig. 2 illustrates diagrammatically the penetration of the various layers into each other, which it appears will produce a new combined layer of Bi, Cs and Ag as indicated by the symbols A and 0 respectively.

If a photo electric cathode or a secondary electron emitting electrode of greater thickness is desired which has the same relative sensitiveness, a layer of alkali metal, as for instance caesium (Cs) may be applied on top of the thin metal layer Bi, as shown in Fig. 3. The alternate application of a thin metal layer having a lower conductivity than the alkali metal and an alkali metal layer may be repeated a number of times, as illustrated in Fig. 4 until a photo electric cathode or secondary electron emitting electrode of the desired thickness is produced.

The layers of the present invention are also suitable for the purposes of thermic emission.

What I claim is:

-1. A photo electric cathode comprising a silver base, a layer of an alkali metal thereon, and a thin layer of antimony forming the top coating of said alkali metal layer.

2. A photo electric cathode comprising an electrically conductive metal base, a layer of an alkali metal thereon, a thin layer of a metal having a lower electric conductivity than said alkali metal on top of said alkali metal layer, and on top of said thin metal layer another layer formed of said alkali metal.

3. A photo electric cathode comprising an electrically conductive metal base, a layer of an alkali metal thereon, a thin layer of a metal having a lower electric conductivity than said alkali metal on top of said alkali metal layer, and a plurality of superposed alternate layers of said alkali metal and said lower conductive metal on top of said first mentioned thin metal layer,

PAUL GORLICH. 

